1. Field of the Invention
The present invention relates to a chemical vapor deposition process and a chemical vapor deposition system that can be used for the production of semiconductors or the like. More particularly, the present invention relates to a process for forming a silicon nitride film on the surface of a semiconductor substrate by means of vapor phase deposition, and to a system for use with the process.
2. Related Art
In order to grow a silicon nitride (SiNx) film on the surface of a semiconductor substrate, there has conventionally been employed a CVD (Chemical Vapor Deposition) process or the like, usually using dichlorosilane and ammonia as feed gases. This is because such a process can give thin films excellent in step coverage inside trenches and in thickness uniformity of wafers.
However, when dichlorosilane and ammonia are used as feed gases, ammonium chloride is produced as the reaction product. Dichlorosilane and ammonia react with each other to give said compound such as ammonium chloride at room temperature when they are simply mixed, so that, when they are fed to a reaction chamber after being mixed, those pipes which are connected to the reaction chamber tend to be clogged and solid particles are also fed to the reaction chamber with feed gases.
Therefore, the mixing of dichlorosilane and ammonia has conventionally been conducted just before the reaction chamber, as close to it as possible, or inside the reaction chamber. In this case, however, those pipes, valves or pumps which are laid or placed after the reaction chamber tend to be clogged.
Further, the ammonium chloride can remain on wafers as particles, and this would be the cause of lowering of yield in the production of semiconductor devices.
Furthermore, the ammonium chloride is unfavorably deposited on exhaust tubes or pumps, so that production systems require periodic maintenance. The productivity of the systems thus becomes low.
In order to solve the foregoing problems, there has been attempted to use monosilane and ammonia in combination as feed gases. However, with this combination, although ammonium chloride is not produced, it is difficult to obtain thin films excellent in coverage and in thickness uniformity.
Under these circumstances, in order to produce thin films excellent in coverage and in thickness uniformity at high productivity, there have been demanded a process and a system for producing silicon nitride films, free from the lowering of yield that would be caused by ammonium chloride, or a process and a system for forming silicon nitride films without producing ammonium chloride.
A first chemical vapor deposition process according to the present invention is such that a silicon compound and a compound selected from the group consisting of hydrazine and derivatives thereof are used as feed gases to form a silicon nitride film on a substrate having recess and/or projection.
A second chemical vapor deposition process according to the present invention is a process for growing a silicon nitride film on a substrate by using, as feed gases, a silane compound and ammonia and derivatives and/or hydrazine and derivatives, in which the halogenated silane compound and the NH3 are preliminarily reacted with each other, and the resulting reaction gas mixture is fed after the ammonium halide produced by the preliminary reaction has been removed from the reaction gas mixture, thereby forming a silicon nitride film on the substrate.
A third chemical vapor deposition process of the present invention is such that a compound containing both silicon and nitrogen is used as a feed gas to form a silicon nitride film on a substrate.
Further, a chemical vapor deposition system of the present invention comprises:
a feeder for a silane compound,
a feeder for ammonia or its derivatives or hydrazine or its derivatives,
a preliminary reaction chamber for carrying out a preliminary reaction between the silane compound and the ammonia or hydrazine derivatives,
an apparatus for eliminating, from the reaction gas mixture, the solid compound such as ammonium halide produced by the preliminary reaction carried out in the preliminary reaction chamber, and
a reaction chamber for forming a silicon nitride film on a substrate placed in the chamber by using the reaction gas mixture from which the solid compound such as ammonium halide has been eliminated.
According to the present invention, it is possible to drastically improve yield in the production of semiconductor devices in which silicon nitride films are formed on substrates by means of chemical vapor deposition, and the productivity of systems for producing semiconductor devices.
According to one aspect of the invention, there has been provided, a chemical vapor deposition process including the steps of: feeding to a reaction chamber a feed gas containing a compound selected from the group consisting of SiH4xe2x88x92x(NH2)x, where xxe2x89xa72, Si(NH)2, (SiH2NH)x, where xxe2x89xa71, (Si2NH)x, where x greater than 1, and NH2(SiH2NH)xSiH2NH2, where x xe2x89xa71, and forming a silicon nitride film on a substrate placed in the reaction chamber using the feed gas.